The field of the invention relates to an improved latch system for use in a disc drive and more particularly to means for optimizing the resting position of the actuator in the landing zone.
In rotating, non-removable data disc storage devices, a data read/write transducer flies upon a air cushion or bearing in extremely close proximity to the data surface. In many disc drives, particularly those which are of extremely small size, the transducer lands upon and takes off from a predefined landing region, typically located near the center of the disc where the disc is mounted to spindle hub of a spindle hub for rotation. It is possible, when shocks are applied to the disc drive, that the transducer can move or bounce across the surface causing erosion or scarring of the magnetic film coating on the disc surface and leading to hard and soft data failures. In addition, a hard transducer head may dent the surface in response to sharp jarring forces attributable to sharp or rough force handling of the drive. As mentioned above, the transducer flies on an air cushion or bearing as created by the constant speed, high speed rotation of the disc. The characteristics of this air flow have been analyzed and discussed in the prior art as shown for example in U.S. Pat. No. 4,467,997 to Westwood and the IBM Journal of Research and Development 1974 pages 480-488.
As a result of these studies, aerodynamically actuated latches have been designed, analyzed and discussed in the prior art is cited above as well as in U.S. Pat. No. 4,538,193. Such latches have proven difficult to incorporate effectively into small size disc drives. The air vane latch and its location on the base plate adjacent to the disc, as well as the fact that the vane must have an extended latching arm which extends across a pivot to capture the actuator arm, contributes to a build up of tolerances in the air vane assembly itself, the location of the latch, the location of the actuator arm and the like. This leads to significant variations in the head landing position on the disc when it is desired to locate and latch the head gap in the landing zone. In turn, this will result in the loss of usable media space for recording data; additional radial space must be devoted to the landing zone where the head will land and rest because of these accumulated tolerances.
Therefore, a general object of the present invention is to overcome the limitations and drawbacks associated with present aerodynamically operated latches used with transducer actuator assemblies in a disc drive.
A further object of the invention is to provide an effective aerodynamic transducer latch mechanism within the confines of a miniaturized disc drive structure which does not introduce an accumulation of tolerances such that the actuator arm cannot be accurately parked in a limited landing zone region on the inner radius of the disc.
A further objective of this invention is to provide a latch design which integrates the aerodynamic latch and the actuator arm which it is intended to latch in place so that the aerodynamic latch when it is in its locking position accurately and reliably holds the actuator arm in a very accurately fixed and stable position on the surface of the disc.
According to one aspect of the invention, there is provided an improved latch system for use in a disc drive including an improved means for eliminating tolerances in the parked position of the actuator arm in the landing zone on the disc. According to this system, the latch system includes latch arm having a rotary engaging portion which engages a portion of the transducer support arm or actuator arm in the disc drive to prevent movement of the transducer when the shock appears; this latch arm is directly coupled to an air vane which extends parallel to the edge of the disc in a region nearly adjacent to the actuator arm and at a distance at a center of the disc which is just greater than the radius of the disc so that the vane extends partially along an arc or a line near to the edge of the disc. The latch arm and vane are arranged so that in the presence of disc rotation, wind generated by the disc presses against the vane, and the vane moves away from the disc. As it does so, the latch arm disengages the actuator arm, allowing it to move freely back and forth over the surface of the disc to locate the transducer over various tracks. When disc rotation ceases, the vane returns to its position adjacent the edge of the disc, and the transducer arm returns the transducer to the landing zone. When it does so, a pin which rises above the surface of the actuator arm engages the end of the latch arm. This pin rests against the end of the actuator arm and prevents further movement of the actuator arm under shock.
Under normal conditions the accumulated tolerances between the final position of the wind vane, the latch arm, the pin, and the actuator arm which supports the pin would all need to be allowed for in defining the landing zone of the arm. According to the present invention however, an adjustable cam pin having a variable outer radius is supported on the actuator arm. When the assembly of the latch arm and actuator arm are complete the pin is rotated so that it rests firmly against the end of the latch arm; in this position, when the wind vane is at rest, the transducer supporting actuator arm rests exactly on the predefined landing zone, and assembly tolerances which would normally have to be incorporated into the landing zone can be eliminated.